What is the relationship between generics and arrays in Java?

The correct answer is B: Generic arrays are not supported; you cannot create arrays of parameterized types. Java does not allow creation of arrays with parameterized types due to type erasure. List[] would be unsafe. You must use List[] or List[] instead.

In a multi-threaded Spring application with singleton beans, what thread-safety consideration must be kept in mind?

The correct answer is B: Developers must ensure singleton bean implementations are thread-safe. Spring doesn't enforce thread-safety for singleton beans. Developers must implement thread-safe code, use immutable objects, or utilize synchronization where necessary.

Which feature of Java ensures that a child class can have a method with a wider return type than the parent class?

The correct answer is B: Method Overriding with Covariant Return Types. Covariant return types (Java 5+) allow a method to return a subtype of the parent class method's return type. For example, if parent returns Animal, child can return Dog (subclass of Animal).

Which statement about wildcard generics (?) is correct?

The correct answer is A: ? represents an unknown type and can be used with upper bounds (? extends T) or lower bounds (? super T). Wildcards (?) represent an unknown type. Upper bound (? extends T) accepts T or its subtypes. Lower bound (? super T) accepts T or its supertypes.

What does the removeIf() method in Collection interface do?

The correct answer is B: Removes all elements matching predicate. removeIf(Predicate) removes all elements that satisfy the given predicate condition (Java 8+).

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Java Programming
JDBC

Java OOP, collections, multithreading

29 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 29

Topics in Java Programming

All Basics & Syntax 100 OOP in Java 100 Collections Framework 100 Multithreading 100 Exception Handling 100 I/O Streams 100 JDBC 100 Generics 100 Lambda Expressions 100 Spring Framework Basics 58

Q.11 Easy JDBC

What is the correct syntax to load a JDBC driver in Java?

A DriverManager.loadDriver('com.mysql.jdbc.Driver');

B Class.forName('com.mysql.jdbc.Driver');

C Driver.load('com.mysql.jdbc.Driver');

D Connection.loadDriver('com.mysql.jdbc.Driver');

Correct Answer: B. Class.forName('com.mysql.jdbc.Driver');

EXPLANATION

Class.forName() is the standard way to load JDBC drivers. It dynamically loads the driver class.

Test

Q.12 Easy JDBC

Which JDBC API is used to execute parameterized queries safely?

A Statement

B PreparedStatement

C ResultSet

D MetaData

Correct Answer: B. PreparedStatement

EXPLANATION

PreparedStatement allows parameterized queries using placeholders (?) and prevents SQL injection attacks.

Test

Q.13 Easy JDBC

Which interface in JDBC is used to execute SQL queries and retrieve results?

A Statement

B Connection

C ResultSet

D Driver

Correct Answer: A. Statement

EXPLANATION

Statement interface is used to execute SQL queries. Connection creates statements, ResultSet holds results, and Driver manages connections.

Test

Q.14 Easy JDBC

What is the purpose of the Connection.commit() method in JDBC?

A To establish a new database connection

B To permanently save all changes made in the current transaction

C To execute the next SQL statement

D To close the database connection

Correct Answer: B. To permanently save all changes made in the current transaction

EXPLANATION

commit() finalizes the transaction and persists all changes made since the last commit or rollback.

Test

Q.15 Easy JDBC

In JDBC, which exception is thrown when the database driver class is not found?

A SQLException

B ClassNotFoundException

C DriverNotFoundException

D DatabaseException

Correct Answer: B. ClassNotFoundException

EXPLANATION

ClassNotFoundException is thrown when Class.forName() cannot locate the JDBC driver class.

Test

Q.16 Easy JDBC

What does the DriverManager.getConnection() method return?

A A Statement object

B A Connection object

C A ResultSet object

D A DatabaseMetaData object

Correct Answer: B. A Connection object

EXPLANATION

DriverManager.getConnection() establishes a connection to the database and returns a Connection object.

Test

Q.17 Easy JDBC

Which JDBC method is used to retrieve the number of rows affected by an INSERT, UPDATE, or DELETE statement?

A getRowCount()

B executeUpdate()

C getUpdateCount()

D fetchSize()

Correct Answer: B. executeUpdate()

EXPLANATION

executeUpdate() returns an int representing the number of rows affected by the SQL statement execution.

Test

Q.18 Easy JDBC

What is the primary advantage of using PreparedStatement over Statement in JDBC?

A Better performance and protection against SQL injection

B Ability to execute multiple queries simultaneously

C Automatic connection pooling

D Direct transaction management

Correct Answer: A. Better performance and protection against SQL injection

EXPLANATION

PreparedStatement pre-compiles SQL and uses parameterized queries, preventing SQL injection and improving performance.

Test

Q.19 Easy JDBC

Which interface in JDBC is used to execute a single SQL statement and return a ResultSet?

A Statement

B PreparedStatement

C CallableStatement

D Connection

Correct Answer: A. Statement

EXPLANATION

Statement interface is used to execute simple SQL queries without parameters and return results as ResultSet.

Test

Q.20 Easy JDBC

What happens when you call rs.next() on a ResultSet after the last row?

A Returns true and loops back to the first row

B Returns false

C Throws a SQLException

D Remains on the last row

Correct Answer: B. Returns false

EXPLANATION

The next() method returns false when there are no more rows available. It does not throw an exception or loop back; it simply indicates that there are no additional rows to traverse.

Test

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